遮罩层位position:fixed定位
弹框为position:absolute定位
弹框弹起时
$("html,body").css({
"width": "100%",
"height": "100%",
"overflow": "hidden",
"position": "fixed"
})
弹框关闭时
$("html,body").css({
"width": "auto",
"height": "auto",
"overflow": "auto",
"position": "static"
})